I have a Dell Inspiron 9400 with Intel 82801G (ICH7) chipset (STAC9200). It also has Intel HD Audio. Sound works but I'm still facing several strange things. Under Windoze, I can control (on/off) speaker output (the "Beep"), I don't hear the PC speakers when I plug my headphones and the sound is clear.

Under Gentoo (Gentoo Sources 2.6.15-r5) I have no PC speaker control (for the "Beep"), I still hear the speakers even when I plug my headphones in the headphones jack and the sound is always a little bit cracky, i.e. I can hear some very low noise like plops and cracks when I play music - just as if I were playing an old LP album. Alsa mixer (and Gnome Volume Control as well) show the following controls:

Master

PCM

Capture

Capture Mux (twice but it looks like a Gnome bug as I only have it once in alsamixer)

Looked a bit more carefully: I don't have any speaker control under Windows either. All controls are the same on both platforms. IEC958 is the SPDIF output, available through a mini-din connector/splitter._________________Gentoo addict: tomorrow I quit, I promise!... Just one more emerge...
GNU/Linux user #369763

>the sound is always a little bit cracky, i.e. I can hear some very low noise like plops and cracks when I
>play music - just as if I were playing an old LP album.
I have the same problem when using hda_intel, try to load the driver with position_fix=1
(modprobe snd-hda-intel position_fix=1)

>I suppose this loads the module in the first position?
No, it have to do something with DMA pointer position. For me it works with position_fix=1 and 2.
Here are some information from the kernel-documentation. You can play with modprobe snd-hda-intel model=... too.

Each codec may have a model table for different configurations.
If your machine isn't listed there, the default (usually minimal)
configuration is set up. You can pass "model=<name>" option to
specify a certain model in such a case. There are different
models depending on the codec chip.

Model name Description
---------- -----------
ALC880
3stack 3-jack in back and a headphone out
3stack-digout 3-jack in back, a HP out and a SPDIF out
5stack 5-jack in back, 2-jack in front
5stack-digout 5-jack in back, 2-jack in front, a SPDIF out
6stack 6-jack in back, 2-jack in front
6stack-digout 6-jack with a SPDIF out
w810 3-jack
z71v 3-jack (HP shared SPDIF)
asus 3-jack
uniwill 3-jack
F1734 2-jack
test for testing/debugging purpose, almost all controls can be
adjusted. Appearing only when compiled with
$CONFIG_SND_DEBUG=y

Note 2: If you get click noises on output, try the module option
position_fix=1 or 2. position_fix=1 will use the SD_LPIB
register value without FIFO size correction as the current
DMA pointer. position_fix=2 will make the driver to use
the position buffer instead of reading SD_LPIB register.
(Usually SD_LPLIB register is more accurate than the
position buffer.)

Under Gentoo (Gentoo Sources 2.6.15-r5) I have no PC speaker control (for the "Beep"), I still hear the speakers even when I plug my headphones in the headphones jack and the sound is always a little bit cracky, i.e. I can hear some very low noise like plops and cracks when I play music - just as if I were playing an old LP album. Alsa mixer (and Gnome Volume Control as well) show the following controls:

the internal buzzer on the mainboard is controlled directly by a kernel option and bypasses alsa. not sure at the moment where that is configured though. had a tough time last time myself finding it... not sure if this is what you were looking for_________________Pentium M 740 on MSI 915GM SPEEDSTER-FA4, 2x512MB Corsair XMS2 DDR2 667 Memory, Zalman CNPS7000B AlCu, Samsung SpinPoint P120 250GB SATAII, Hauppauge WinTV PVR-500, Enermaxx Liberty 400, Antec P180

the internal buzzer on the mainboard is controlled directly by a kernel option and bypasses alsa. not sure at the moment where that is configured though. had a tough time last time myself finding it... not sure if this is what you were looking for

Or to blacklist the spkr module, which is what I did. It doesn't require recompiling the kernel when you need it._________________Gentoo addict: tomorrow I quit, I promise!... Just one more emerge...
GNU/Linux user #369763

Great... I've just tried Gentoo Sources 2.6.16-r1 and I have no more sound . HPs are silent, as well as my headphones..._________________Gentoo addict: tomorrow I quit, I promise!... Just one more emerge...
GNU/Linux user #369763

Ok, now I've applied the patch mentionned by roynux and I get sound through my headphones only. Main HPs still muted, like you said, roynux. But it's more than nothing. Thanks for the hint._________________Gentoo addict: tomorrow I quit, I promise!... Just one more emerge...
GNU/Linux user #369763

Having an issue with the snd-hda-intel driver using kernel gentoo sources 2.6.16-gentoo-r1. For some reason the HD audio driver was removed from the kernel with r1. It was in 2.6.16. Also, the alsa driver for it is not wanting to install. I keep getting weird issues with the output when I start alsasound.

Things get worse. With either kernels I tried the microphone doesn't work at all. I'm using Skype but all I can do is text-chat. Has anyone else tried the microphone?_________________Gentoo addict: tomorrow I quit, I promise!... Just one more emerge...
GNU/Linux user #369763

Ah, good news. I followed this guide and now I get sound working with 2.6.16-gentoo-r1. And most of all HP are now muted when an earphones jack is plugged in. I still have to check Mic input but at least it works normally for sound output. The trick is to use alsa driver from portage._________________Gentoo addict: tomorrow I quit, I promise!... Just one more emerge...
GNU/Linux user #369763

Ah, good news. I followed this guide and now I get sound working with 2.6.16-gentoo-r1. And most of all HP are now muted when an earphones jack is plugged in. I still have to check Mic input but at least it works normally for sound output. The trick is to use alsa driver from portage.

Problem no more solved entirely after a couple of updates. And it's getting even more wierd...

When I boot my laptop I have to manually restart /etc/init.d/alsasound before I logon into Gnome. Then I get sound from the speakers. If I plug my headphones, the main speakers are muted, normal. However I get sound in Gnome only from multimedia applications; Gnome events remain silent i.e. I don't get any sound for Gnome events (application launch, message boxes, aso).

a) If I logon into Gnome without restarting alsasound, I get no sound in Gnome. I get no sound either from the console.

b) If I restart alsasound directly from Gnome (Ok, I'm playing with fire) I get sound but the headphones don't mute the main speakers anymore! Then Gnome sound events do work!

Go figure..._________________Gentoo addict: tomorrow I quit, I promise!... Just one more emerge...
GNU/Linux user #369763

That guy at Disgruntledgoat.com has gone through the same sound maze. I've added his page to my favorites as he even submitted a bug for the lack of support of Intel HDA._________________Gentoo addict: tomorrow I quit, I promise!... Just one more emerge...
GNU/Linux user #369763